Hans-Jörg Gillmann

Inhibition of protein phosphatase 1 by inhibitor-2 exacerbates progression of cardiac failure in a model with pressure overload

AIMS The progression of human heart failure is associated with increased protein phosphatase 1 (PP1) activity, which leads to a higher dephosphorylation of cardiac regulatory proteins such as phospholamban. In this study, we tested the hypothesis whether the inhibitor-2 (I-2) of PP1 can mediate cardiac protection by inhibition of PP1 activity. METHODS AND RESULTS We induced pressure overload by transverse aortic constriction (TAC) for 28 days in transgenic (TG) mice with heart-directed overexpression of a constitutively active form of I-2 (TG(TAC)) and wild-type littermates (WT(TAC)). Both groups were compared with sham-operated mice. TAC treatment resulted in comparable ventricular hypertrophy in both groups. However, TG(TAC) exhibited a higher atrial mass and an enhanced ventricular mRNA expression of beta-myosin heavy chain. The increased afterload was associated with the development of focal fibrosis in TG. Consistent with signs of overt heart failure, fractional shortening and diastolic function were impaired in TG(TAC) as revealed by Doppler echocardiography. The contractility was reduced in catheterized banded TG mice, which is in line with a depressed shortening of isolated myocytes. This is due to profoundly abnormal cytosolic Ca(2+) transients and a reduced stimulation of phosphorylation of phospholamban (PLB)(Ser16) after TAC in TG mice. Moreover, administration of isoproterenol was followed by a blunted contractile response in isolated myocytes of TG(TAC) mice. CONCLUSION These results suggest that cardiac-specific overexpression of a constitutively active form of I-2 is deleterious for cardiac function under conditions of pressure overload. Thus, the long-term inhibition of PP1 by I-2 is not a therapeutic option in the treatment of heart failure.

Perioperative levels and changes of high-sensitivity troponin T are associated with cardiovascular events in vascular surgery patients.

Objectives:Myocardial infarction after major surgery is frequent, drives outcome, and consumes health resources. Specific prediction and detection of perioperative myocardial infarction is an unmet clinical need. With the widespread use of high-sensitive cardiac troponin T assays, positive tests become frequent, but their diagnostic or prognostic impact is arguable. We, therefore, studied the association of routinely determined pre- and postoperative high-sensitive cardiac troponin T with the occurrence of major adverse cardiac events. Design:This study was a prospective noninterventional trial. Setting:This study was conducted at Hannover Medical School in Germany. Patients:A total of 455 patients undergoing open vascular surgery were followed for 30 days for the occurrence of major adverse cardiac events. Interventions:None. Measurements and Main Results:Preoperative and 24-hour postoperative high-sensitive cardiac troponin T measurements and the respective changes were correlated to medical history and the occurrence of major adverse cardiac events (cardiovascular death, myocardial infarction, and ischemia). Pre- and postoperative high-sensitive cardiac troponin T measurements demonstrated a majority of patients with detectable troponin levels preoperatively and an increase over the 24 hours after surgery. The level of high-sensitive cardiac troponin T was significantly associated with preexisting diseases that constitute the Lee’s Revised Cardiac Risk Index. A preoperative high-sensitive cardiac troponin T greater than or equal to 17.8 ng/L and a perioperative high-sensitive cardiac troponin T change greater than or equal to 6.3 ng/L are independently associated with the occurrence of major adverse cardiac events. Adding high-sensitive cardiac troponin T absolute change to the Revised Cardiac Risk Index improves the risk predictive accuracy of the score as evidenced by increased area under receiver operating characteristic and significant reclassification effects. Conclusions:The risk predictive power of high-sensitive cardiac troponin T change in addition to the Revised Cardiac Risk Index could facilitate 1) detection of patients at highest risk for perioperative myocardial ischemia, 2) evaluation and development of cardioprotective therapeutic strategies, and 3) decisions for admission to and discharge from high-density care units.

Thrombomodulin's lectin-like domain reduces myocardial damage by interfering with HMGB1-mediated TLR2 signalling

AIMS Thrombomodulin (TM), via its lectin-like domain (LLD), exhibits anti-inflammatory properties partly by sequestering the pro-inflammatory cytokine, high-mobility group box 1 (HMGB1). Since myocardial damage after ischaemia and reperfusion is mediated by inflammation, we evaluated the cardioprotective effects of the LLD of TM. Using an in vivo mouse model of transient ischaemia and in vitro models of cardiomyocyte hypoxia, we assessed the ability of the LLD to suppress HMGB1-mediated activation of the receptors, receptor for advanced glycation endproducts (RAGEs) and Toll-like receptors (TLRs) 2 and 4. METHODS AND RESULTS Thirty-minute myocardial ischaemia was induced in isoflurane-anaesthetized mice followed by 24 h of reperfusion in wild-type (WT) mice, in mice lacking the LLD of TM (TM(LeD/LeD) mice), and in WT with systemic overexpression of the LLD of TM induced by hydrodynamic transfection. Infarct size, HMGB1 protein, and apoptotic cells were significantly increased in TM(LeD/LeD) mice when compared with WT. Neonatal rat cardiomyocytes transfected with TLR2-, TLR4-, and RAGE-siRNA were exposed to hypoxia (0.8% O2) and reoxygenation (21% O2). HMGB1 augmented hypoxia-induced apoptosis in TLR2- but not in RAGE- or TLR4-suppressed cells. Administration of HMGB1- and TLR2-blocking antibodies in TM(LeD/LeD) mice prior to myocardial ischaemia diminished apoptosis. Therapeutic systemic gene therapy using the LLD reduced the infarct size and HMGB1 protein levels 24 h after reperfusion. CONCLUSION The LLD of TM suppresses HMGB1-induced and TLR2-mediated myocardial reperfusion injury and apoptosis in vitro and in vivo.

Lidocaine Protects from Myocardial Damage due to Ischemia and Reperfusion in Mice by Its Antiapoptotic Effects

Background:Perioperative myocardial ischemia poses a vital threat to surgical patients. Means to protect postischemic myocardium are clinically not available. Lidocaine has been demonstrated to exert antiinflammatory pleiotropic effects. The authors set out to test if lidocaine protects ischemic myocardium from reperfusion injury. Method:A mouse model of transient coronary artery ligation (30 min) and reperfusion (24 h) was used with animal care committee approval. Infarct size and area-at-risk were determined. Leukocyte recruitment was quantified on immunohistochemical stainings. Apoptosis was assessed using enzyme-linked immunosorbent assay to detect histone modifications and terminal deoxynucleotidyl transferase dUTP nick end labeling assays. Lidocaine effects on leukocyte-endothelial interactions were assessed in vitro by using a parallel-plate flow chamber or static adhesion assays. Results:Infarct size per area-at-risk was reduced by 27% in mice treated with a lidocaine bolus (1 mg/kg) before a continuous infusion (0.6 mg · kg–1 · h–1) during ischemia (P < 0.005). Neutrophil density in the infarct and periinfarct zone was not reduced by lidocaine, although the size of the infiltrated area was. Terminal deoxynucleotidyl transferase dUTP nick end labeling–positive cardiomyocytes and endothelial cells were significantly reduced in the periinfarct zone by lidocaine. In vitro, no effect on leukocyte rolling or firm adhesion to resting or activated endothelium was demonstrable. In vitro, lidocaine reduced cardiomyocyte apoptosis induced by hypoxia and reoxygenation (3h/1h) significantly. Infarct size and in vitro cardiomyocyte apoptosis were likewise reduced when lidocaine bolus and infusion were administered after the ischemic insult. Conclusion:Lidocaine exerts cardioprotective effects when administered before or after the ischemic insult. This effect is mediated through an antiapoptotic and not through an antiinflammatory pathway and may be therapeutically exploitable.

Infection-associated platelet dysfunction of canine platelets detected in a flow chamber model

BackgroundIn the present study, the influence of bacterial infection, lipopolysacharides (LPS) and hydroxyethyl starch (HES) on platelet function in a parallel plate flow chamber were measured. Experiments were performed with non-activated and protease-activating-receptor (PAR) 4 agonist activated platelets. Comparative measurements were in vivo capillary bleeding time, platelet function analyzer and impedance aggregometry.ResultsPAR 4 agonist did not increase platelet adhesion of platelets from dogs with bacterial inflammation in the flow chamber in contrast to platelets of healthy dogs. Except from impedance aggregometry with lower sensitivity and specificity, PFA did not detect platelet dysfunctions in dogs with infection. In vitro addition of LPS or HES significantly reduced platelet covered area after PAR-activation.ConclusionsThe flow chamber detects platelet dysfunctions in dogs with inflammatory diseases. In vitro addition of LPS highlights the inhibiting effect of bacterial wall components on platelet function. Platelet dysfunction induced by infection could possibly also be diagnosed after treatment of sepsis with colloids has commenced. The flow chamber could be a useful tool to detect sepsis associated platelet dysfunction given that larger prospective trials confirm these findings from a proof of concept study.

Adrenomedullin Is Associated With Surgical Trauma and Impaired Renal Function in Vascular Surgery Patients.

Background: Patients undergoing vascular surgery are prone to perioperative organ injury because of both higher prevalence of cardiovascular risk factors and the extent of surgery. Early detection of organ failure is essential to facilitate appropriate medical care. Midregional pro-adrenomedullin (MR-proADM) has been investigated in acute medical care settings to guide clinical decision-making regarding patient pathways and to identify patients prone to imminent cardiovascular or inflammatory complications. In this study, we evaluated the impact of perioperative MR-proADM levels as an early marker of perioperative cardiovascular and inflammatory stress reactions and kidney injury. Methods: The study was conducted as a monocentric, prospective, noninterventional trial at Hannover Medical School, Germany. A total of 454 consecutive patients who underwent open vascular surgery were followed from the day prior to until 30 days after surgery. The composite primary end point was defined as the occurrence of major adverse cardiac events (MACEs), acute kidney injury (AKI), or systemic inflammatory response syndrome (SIRS). Measurements were correlated with both medical history and postoperative MACE, AKI, or SIRS using univariate and multivariate regression analysis. Results: One hundred thirty-nine (31%) of the patients reached the primary end point within the study interval. Midregional pro-adrenomedullin change was associated with the combined primary end point and with the intensity of surgical trauma. Midregional pro-adrenomedullin change was increased in patients reaching the secondary end points, SIRS (optimal cutoff: 0.2 nmol/L) and AKI (optimal cutoff: 0.7 nmol/L), but not in patients with MACEs. Conclusion: Increased levels of MR-proADM within the perioperative setting (1) were linked to the invasiveness of surgery and (2) identified patients with ongoing loss of renal function. Increased MR-proADM levels may therefore identify a subgroup of patients prone to excessive cardiovascular stress but did not directly correlate with adverse cardiac events. Consistently low levels of MR-proADM may identify a subgroup of patients with acceptable low risk to guide discharge from high-density care units.